Electrical relay



July 1 57 H. Y. FISHER 2,798,916

ELECTRICAL RELAY Filed Sept. 3, 1953 2 Sheets-Sheet l MW .Hamfm 2775/742" July 9, 1957 H. Y. FISHER ELECTRICAL RELAY 2 Sheets$heet 2 FiledSept. 3, 1953 will 2. F/i/W ELECTRECAL RELAY Hardin Y. Fisher, Hillside,111., assignor, by mesne assignrnents, to Controls Company of America,Schiller Park, 11]., a corporation of Delaware Application September 3,1953, Serial No. 378,373

4 Claims. (Ci. 20%87) This invention relates to electrical relays andrefers more particularly to a relay of the type which responds to smallvariations in power and which has a coil mounted upon a U-shaped frame,between the legs thereof, and an armature extending across the open endof the frame and fulcrumed on ledges on one leg of the frame forswinging motion toward and from a pole piece located between theextremities of the frame legs.

Relays of the type here under consideration are designed to open andclose a power circuit in response to relatively small changes in thevalue of current in a control circuit in which the coil of the relay isconnected. For example, such a relay may be required to close when itscoil is energized by about 0.1 watt and to open when the power drops toabout .01 watt. In order to achieve this responsiveness to small changesin current value (as distinguished from energization and completede-energization of the coil), together with the necessary snap action ofthe contacts, it is essential to regulate very precisely both the airgap between the armature and the pole piece of the coil and the pressurewith which the fixed and movable contacts are engaged in the attractedposition of the armature.

Heretofore it has been considered impossible to attain such accurateestablishment of the air gap by means of ordinary production methods.The reason for this will be apparent in the light of the fact that atolerance of about .00075 inch must be maintained in the air gap in thecase of a relaywhich will be responsive to the power values mentioned.

Where the attracted position of the armature was defined by theengagement of the underside of its free end against the end of the frameleg opposite that upon which the armature was fulcrumed, the framesurface which faced the underside of the armature had to bepainstakingly finished with respect to the fulcrum points and the poleface to obtain the desired air gap and, moreover, had to be perfectlystraight and parallel with the ledges upon which the armature wasfulcrumed. In addition, the armature had to be absolutely flat anduntwisted; otherwise the armature would assume a virtually unpredictableattracted position, depending upon the extent to which it tiltedlaterally in seating upon the frame stop in response to the magneticattractive forces upon the armature.

A simpler expedient, therefore, for regulating the size of the air gapin such relays was the use of a non-magnetic set screw threaded into thearmature for engagement with the pole piece in the fully attractedposition of the armature. However, adjustment of this set screw toregulate the air gap unavoidably resulted in a varia tion of contactpressure.

Ordinarily the armature carries at least one movable contact which iscooperable with afixed contact on the leg of the frame opposite that onwhich the armature, is fulcrurned. One of the two contacts isresiliently mo d; fo xamp e, th m va le con t y be Q "ice 7 2,798,916Fatentecl July 9, 1957 mounted on the end of a spring arm carried by thearmature. The fixed contact is so mounted that the movable contactengages it before the armature attains its fully attracted position, sothat the spring arm is required to flex in the final stages of suchmotion of the armature, and the two contacts will therefore be heldtogether under a pressure determined by the amount of fiexure of thespring arm. Thus, for example, if the air gap was increased by turningthe set screw downwardly, contact pressure was decreased. Moreover,because contact pressure was determined in part by the position of theend of the spring arm when the same was unflexed, any slight initialcurvature of the spring arm imparted thereto during the manufacturingand assembling operations resulted in a further and unpredictablevariation in con tact pressure.

With the problems of precise control of air gap dimension and contactpressure in mind, it is an object of the present invention to provide anelectromagnetic relay of the character described which is so constructedthat a very simple and expeditious adjusting step in the final assemblyof the relay will enable simultaneous but independent establishment ofthe precise air gap desired and the exact contact pressure required,regardless of variations in the dimensional accuracy of the relaycomponents such as are normally encountered in mass production, andregardless of whether one or two sets of contacts are provided.

Another object of this invention resides in the pro-. vision of anelectromagnetic relay of the character de scribed which is not dependentupon adjustment of a set screw for the establishment of the required airgap dis tance, but wherein both the air gap dimension and the contactpressure may be independently but very accurately established by thesimple tightening of two securement screws during final assembly of therelay.

Another object of this invention resides in the provision of a stop forthe armature comprising, in effect, an extension of one leg of the relayframe which is so mounted thereon as to be adjustable in oppositedirections normal to the plane of the pole face to enable said stop tobe moved against the underside of the armature when the latter is heldprecisely spaced the desired distance from the pole face, as by a shim,and to enable the stop to be readily secured to the frame leg in theposition of the stop thus established to fix the desired air gap. Theadjustability of the armature stop, of course, also enables the size ofthe air gap to be changed at will to suit almost any other pullain anddrop-out values.

In this connection it is a-further object of the invention to prov de ,arelay wherein engagement between the armature and its stop is confinedto a pair of spaced apart localized points. Such localized engagement ofthe armature with its stop may be effected by coining either the stop orthe armature, or both, and it will be appreciated that this expedienteliminates the necessity for flattening the armature to overcome anywarpage thereof occur ring as the result of punching or shearing thearmature. More over, since the area of contact between the armature andits stop affects the drop-out characteristics of a relay of the typehere under consideration, the expedient of limiting such engagement toonly a pair of localized points enables the area of engagement to beheld as near- 1y constant as possible so as to achieve the greatestconsistency of operating characteristics with a given air gap betweenthe armature and the pole piece.

With the above and other objects in view, which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiment of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure l is a side elevational view of an electromag- Z Figure 5 is apartial vertical sectional view of the relay shown in Figure 4.

Referring now more particularly to the accompanying drawings, in whichlike numerals designate like parts throughout the several views, thenumeral 5 designates generally an electromagnetic relay embodying theprinciples of this invention and having a coil or winding 6 mountedbetween the legs of a magnetically permeable, substantially U-shapedframe 7, with the axis of the coil extending parallel to the legs of theframe. The frame is preferably formed from flat strip material, as is amounting base 8 to which the frame is secured. A pole piece 9 betweenthe extremities of the frame. legs comprises the enlarged head of arod-like magnetically permeable core member which extends downwardlythrough the coil. The head overlies the upper end of the coil, while thecore has a reduced lower end portion extending through aligned holes inthe closed end of the frame and the base and peened over, as at 10, tosecure the coil to the frame and also to secure the mounting base 8 tothe bottom of the relay structure.

A flat armature 11, stamped or otherwise formed from permeable stripmaterial, is fiatwise fulcrumed at one end portion on a pair of ledges12 on the rear leg 13 of the frame, with the armature spanning the openend of the frame and swingable toward and from the pole piece 9. Lateraland endwise displacement of the armature olf of the frame is precludedby a pair of tongues 14 comprising integral upward extensions of therear frame leg, at the sides thereof, which extend through looselyfitting slots 15 in the armature opening to the side edges of the latternear the rear thereof. Upward displacement of the armature is precludedby a flat, thin finger 16 which is secured to the rear face of the rearframe leg, intermediate the side edges thereof, and which projectsupwardly through a medial slot 18 in the armature between and slightlyto the rear of the slots 15 therein. At its top the finger 16 terminatesin an arrow-like head 19 which is wider than the slot 18. The slot 18 inthe armature opens forwardly to an aperture 21 which is in line with theslots 15 and which is wide enough to clear the arrow-shaped head on thefinger. Thus when the armature is placed on the ledges 12 beneath thetop surface of the rear frame leg and between the tongues 14, and withthe finger extending straight up, the arrowhead 19 readily passesthrough the aperture 21, and the finger may then be bent rearwardly tocarry its reduced upper end portion beneath the arrowhead into the slot18 to a position where the downwardly facing shoulders on the arrowheadwill block upward displacement of the armature.

The rear end portion of the armature provides an anchor 22 for the upperend of a coiled tension spring 23. The lower end of the spring isanchored to the lower end portion of the finger 16, which is bentrearwardly substant-ially at right angles to the plane of the leg 13, asat 24. The spring, of course, tends to rock the armature on the fulcrumprovided by the ledges 12, in a direction away from its attractedposition.

Movable contacts 25 are carried on the ends of elongated spring arms 26and cooperate with fixed contacts 27 mounted on the front leg 28 of theframe in a manner described hereinafter. The spring arms are, in turn,secured to a strip of insulative material 29 fastened to the armaturejust ahead of its fulcrum as by means of rivets, and the arms aredisposed at the opposite side edges of the armature, preferably spacedoutwardly therefrom. On an insulative terminal strip 30 secured to theouter face of the rear frame leg 13 are mounted power circuit terminals32 which are connectable with a circuit to be controlled by the relayand which are electrically connected with the spring arms by shortlengths of soft, flexible wire 33. The rivets 34 which secure theinsulative terminal strip 30 to the rear frame leg may also fasten thefinger 16 thereto.

Each of the fixed contacts 27 is mounted on the top of a conductive post35 which is secured, as by means of rivets 36, to an insulative mountingmember 37. The conductive posts are inverted L-shaped strips havingtheir stem portions extending upwardly parallel to one another andspaced apart a distance corresponding to the distance between the springarms 26, and a fixed contact is secured on the rearwardly extending baseportion 38 of each post. The insulative mounting member 37 has a pair ofvertically elongated slots 39 through which-screws 40 pass somewhatloosely to be received in threaded holes 41 in the front frame leg 28.The screws secure the mounting member to the outer side of the frontframe leg and at the same time enable the mounting member to be readilyadjusted up and down as well as tilted edgewise to thus effect accurateadjustment of the contact pressure, as will appear presently. A stop 43,comprising an inverted L-shaped strip of metal, with the base 44 of theL extending rearwardly over the front portion of the armature, is alsosecured to the mounting member 37, between the conductive posts, anddefines the fully retracted position of the armature wherein the uppersurface of the armature engages the stop.

In the relay of this invention the front frame leg terminates asubstantial distance below the upper end of the coil, and the fullyattracted position of the armature is defined by a stop comprising thetop surface of a permeable extension 45 of the front frame leg 28 whichprovides for adjustment of the air gap. The extension 45 has the shapeof an inverted L, with its flange 46 providing the armature stop beneaththe front portion of the armature. The stem 47 of the extension isprovided withvertical slots 48 that align laterally with the slots 39 inthe insulative mounting member 37. The same screws 40 which secure theinsulative mounting member to the front frame leg also extend somewhatloosely through the slots 48 in the extension 47 to secure it in placeon the front frame leg. It will be seen that as the permeable extension47 is adjusted up and down on the frame the position of its flange 46will determine the size of the air gap between the armature and the polepiece.

In order to decrease the area in which the armature and its. stop are incontact with one another when the armature is in its fully attractedposition, the two are caused to engage only at two relatively smallareas adjacent to their side edges by reason of the fact that the flange46 of the permeable extension has a pair of laterally spaced, relativelysmall bumps or protrusions 49 coined upwardly therefrom while thearmature has downwardly coined flats 51 on its marginal side edgeportions in positions to engage the protrusions on the extension. Itshould be understood, however, that it is not essential to coin both thearmature and its stop in order to assure the desired limited contacttherebetween. Equally good results are obtained, for instance, when onlythe flange 46 comprising the armature stop is coined to provide it withthe two'npwardly projecting bumps or protrusions 49, which havesufficient height to overcome any warpage in the armature that may haveresulted from stamping or shearing the same from sheet stock. 0n theother assi tahand, if the top surface of the armature stop is relativelystraight and flat, only the armature may be coined to provide it withthe downwardly projecting flats 51 on its marginal side edge portions.relay of the type herein concerned, the area of contact between thearmature and its stop has a relatively great effect upon the drop-outcharacteristics of the relay. Hence, if contact is confined to two smalllaterally spaced locations along the underside of the armature, theseareas can be made as close to constant as possible to achieve thegreatest consistency of operating characteristics with relays having agiven air gap between their armatures and pole pieces.

When the relay of this invention is assembled, the two screws 40 arevery loosely inserted into the front frame leg so that both theinsulative mounting member 37 and the extension 45 are held in placethereon in such a manner as to be freely slidable up and down, andedgewise tiltable, independently of one another. The air gap and contactpressure may thenbe readily established by the very simple operationillustrated in Figure 4. A shim 53, preferably of magnetically permeablemetal and having a thickness exactly equal to the desired air gap isinserted between the pole piece 9 and the underside of the armature; andwith the relay mounted upside down, i. e., armature lowermost, the coilis energized so that the armature will assume the desired fullyattracted position seated against the shim. With the coil so energizedthe extension 45 will of its own weight slide downwardly to bring bothof its protrusions 49 into engagement with the underside of thearmature, and since the permeable shim has a thickness equal to the sizeof the desired air gap, and the armature is therefore occupying itsdesired fully attracted position, the armature stop will likewise assumeexactly the position required to maintain that air gap. Moreover, anytendency of the armature to rock or tilt laterally upon its fulcrum inthe course of its swinging motion in response to energization of thecoil will be fully compensated by reason of the fact that the stop willassume a position to accommodate such rocking or tilting motion. It isfor this reason that it is preferable to retain the armature in itsattracted position by energizing the coil, so as to cause the armatureto seat itself in the same position that it will assume when the relayis placed in service, rather than holding it in its attracted positionby the application of externally applied force thereto.

With the coil energized, the mounting member carrying the fixed contactsis biased downwardly, i. e., toward the armature, with a force equal tothe desired contact pressure. This may be readily accomplished by haning weights 54 on the mounting member, the total weight of the mountingmember and said weights being equal to the desired contact pressure. Tofacilitate this operation holes 55 are provided near the lower ends ofthe conductive posts 35, in which the weights may be hooked and whichalso serve as terminals for power circuit conductors when the relay isinstalled in service. With the mounting member so weighted the fixedcontacts will, of course, engage the movable contacts under a pressurewhich will flex the spring arms carrying the movable contacts to exactlythe position they are required to have in the fully attracted positionof the armature in order to provide the desired contact pressure. It isthen necessary only to tighten the two screws 40 in order to completethe assembly, securing the permeable extension 45 with the armature stopthereon and the contact mounting member 37 in exactly their requiredpositions. After the screws 40 are tightened, varnish or the like isapplied to their extremities to prevent them from loosening during useof the relay.

From the foregoing description, taken together with the accompanyingdrawings, it will be apparent that this invention provides anelectromagnetic relay of the type which is capable of responding torelatively small changes In an extremely sensitive in power and which isso constructed that both the air gap and contact pressure may be veryprecisely determined by high-speed production methods despite inevitableinaccuracies in dimensions of the components within normal massproduction tolerances.

What I claim as my invention is:

1. In a relay of the type having a coil mounted in a U-shaped frame witha pole piece between the legs of the frame and with the coil axissubstantially parallel to the legs of the frame, an armature extendingacross the open end of the frame, hingedly connected at one end to oneleg of the frame to swing toward the pole piece to an attractedposition, and a movable contact carried by the armature cooperable witha fixed contact mounted on the frame, said contacts being engageable inthe attracted position of the armature and one of said contacts beingresiliently mounted, means for precisely adjusting the spacing betweenthe armature and the pole piece in the attracted position of thearmature and for precisely adjusting the pressure with which saidcontacts are engaged in the attracted position of the armature, saidmeans comprising: a screw threaded into the other leg of the frame withits axis transverse to that of the coil; an extension on said other legof the frame having a surface facing the underside of the armature andwith which the armature is engageable to define the attracted positionof the armature, said extension having a slot therein through which saidscrew passes, so that said extension may be freely slid along said leg,in directions parallel to the coil axis, to enable precise establishmentof the air gap between the armature and said pole piece, said extensionbeing retainable in any position to which it is thus moved by tighteningthe screw; and a member upon which said fixed contact is mounted, saidmember having a slot therein through which said screw passes so thatsaid member may be freely slid along said other leg of the frame(independently of said extension) in directions parallel to the coilaxis when the screw is loose to permit said member to be moved to aposition at which the desired contact pressure will obtain by holdingthe armature in its position at which the desired air gap obtains andbiasing the member toward the movable contact with a force equal to thedesired contact pressure, said member being retainable in the positionto which it is thus biased by tightening the screw.

2. In a relay of the type having a coil mounted in a U-shaped frame witha pole piece between the legs of the frame and with the coil axissubstantially parallel to the legs of the frame, an armature extendingacross the open end of the frame, hingedly connected at one end to oneleg of the frame to swing toward the pole piece to an attractedposition, and a movable contact carried by the armature cooperable witha fixed contact mounted on the frame, said contacts being engageable inthe attracted position of the armature and one of said contacts beingresiliently mounted, means for precisely adjusting the spacing betweenthe armature and the pole piece in the attracted position of thearmature and for precisely adjusting the pressure with which saidcontacts are engaged in the attracted position of the armature, saidmeans comprising: an extension for the other leg of the frame having asurface against which the armature is engageable in its attractedposition; means for adjustably mounting said extension on the frameadjacent to said other leg of the frame and with said surface facing theunderside of the armature to be engaged thereby, said mounting meansenabling sliding adjustment of said extension in directions parallel tothe coil axis to enable precise establishment of the air gap between thearmature and said pole piece; a member upon which said fixed contact ismounted; means mounting said member on the frame and permitting saidmember to be freely slidable in directions parallel to the coil axis sothat saio member may be moved to a position at which the desired theopen end of the frame, hingedly connected at one end to one leg of theframe to swing toward the pole piece to an attracted position, and amovable contact carried by the armature cooperable with a fixed contactmounted on the frame, said contacts being engageable in the attractedposition of the armature and one of said contacts being resilientlymounted, means for precisely adjusting the spacing between the armatureand the pole piece in the attracted position of the armature, said meanscomprising: an extension member adjustably mounted on the other leg ofthe frame and having a-surface facing the underside of the armature andengageable by the armature when the armature is in its fully attractedposition, said extension member being movable in directions parallel tothe coil axis; and means for securing said extension member in any ofits positions of adjustment so that the position of its said surface maybe adjusted in directions parallel to the coil axis and retained in aposition in which it will precisely establish the desired air gapbetween the armature in its attracted position and said pole piece.

4; The relay of claim 3, wherein the rigid armature is engageable withsaid surface on the extension, when the armature is in its attractedposition, at two spaced apart points, to preclude lateral rocking of thearmature when it is in said position and thereby assure maintenance of auniform air gap and also to insure consistent operating characteristicsfor the relay.

References Cited in the file of this patent UNITED STATES PATENTS 7281,249 DInfreville July 17,1883 1,785,887 Chryst Dec. 23, 19302,545,835 Wilson et a1. Mar. 20, 1 951 FOREIGN PATENTS I 464,336 GreatBritain Apr. 15, 1937 581,459 Germany July 27, 1933

